1. Field of the Invention
The present invention is directed to an x-ray diagnostics installation having an image intensifier video chain, wherein a region of primary medical interest can be displayed with the overall image.
2. Description of the Prior Art
X-ray installations are known in the art wherein the output image of the x-ray image intensifier is supplied to a video camera, which then supplies the image, with appropriate processing, to a video display. It is also known to intercept the light image with fiber optics having an input end disposed between the image intensifier and the video camera. Individual opto-electric transducers are allocated to the respective light waveguides in the fiber optics system and predetermined transducers are selectively switched (i.e., caused to emit light) so as to form a signal corresponding to the average image brightness in a predetermined region of the overall image.
The detector formed by the transducers may consist of a matrix of photo-elements, with a specific geometrical arrangement of photo-elements being activateable to form an output signal in accordance with the desired region of primary medical interest for controlling the dose rate, and/or for automatically ceasing an x-ray exposure. As a consequence of this structure, such a matrix can only be interrogated in a fixed mode, namely serially, which results in limitations in the interrogation speed.
An x-ray diagnostics installation is disclosed in European Application No. 0 217 456 of the type described above, wherein a plurality of measuring fields having variable shape can be selected, so that the selected measuring field is optimally adapted to the prevailing conditions. This enables a high interrogation speed.